Some patterns constituting a large-scale integrated circuit (LSI), as exemplified by DRAM of a gigabit class, have a minimum feature size on the order of submicron to nanometer. One of major causes for yield reduction in a manufacturing process of such an LSI includes defects on a reticle (also called a mask) used for lithography.
Particularly with increasingly finer pattern dimensions of LSI formed on a semiconductor wafer, dimensions that must be detected as pattern defects are also becoming extremely smaller. Thus, reticle defect inspection apparatuses with high resolution for inspecting for extremely small defects are vigorously being developed.
An effective method of improving resolution is to make wavelengths of inspection light shorter. Thus, DUV (Deep Ultra Violet) light sources providing short wavelengths are increasingly used as light sources for generating inspection light. In addition, it is desirable to obtain high-precision images in order to improve resolution and, for this purpose, it is necessary to irradiate a reticle with a uniform inspection light (or illumination light) using an illuminating optical system of a reticle defect inspection apparatus. To obtain such a uniform inspection light, an effective method is considered to provide an integrator (also called a homogenizer or fly eye lens) in the illuminating optical system (for example, JP-A. 2006-98156(KOKAI)). An integrator is constituted, for example, by bundling a plurality of rod lenses having a length of several dozen mm and a diameter of about 1 mm and a uniform inspection light can be realized by causing a laser light to pass through the integrator.
An object of the present invention is to provide a reticle defect inspection apparatus that can sustain a high-precision defect inspection for a long time and an inspection method using thereof.